Fabrication of discharge devices



Nov. 19, 1946. J, E, BEGGS 4 2,411,184

FABRICATION 0F DISCHARGE DEVICES His Attorney.

Nov, 19, 1946.

J. E. BEGGS FABRICATION 0F DISQHARGE DEVICES Fiied July 2, 1942 2 Sheets-Sheet 2 Patented Nov. 19,- 1946 2,411,184 FABRICATION oF DISCHARGE DEVICES James E. Boggs, Scotia, N. Y., assgnor to General `Electric Company, a corporation of New York Application July 2, 1942, Serial No. 449,391

(Cl. Z50-27.5)

Claims.

This is a continuation-impart of my copending application, Serial No. 436,633, filed March `28, 1941, and assigned to the General Electric Company, a corporation of New York.

The present invention relates to the fabrication of electronic discharge devices and more particularly to a process for obtaining a precise spacing of the electrodes of such devices.

In connection with vacuum tubes for use in the ultra-high frequency range it is important that the interelectrode distances be uniformly 4maintained from tube to tube with a deviation not materially in excess of a fraction of a mil. Any deviation greater than this, especially with reference to the spacing between the cathode and grid electrodes, results in inconsistent and unpredictable operating characteristics and is, therefore, highly undesirable.

It is an object of the present invention to provide a method of tube fabrication by which tolerances as close as those specified can be readily maintained.

One aspect of the invention which is important in the attainment of the foregoing object involves making at least one of the electrodes employed of deformable construction, installing the electrode in approximately its desired location in the tube structure, and thereafter deforming the electrode in situ to bring its active part more precisely into the desired relationship with the other electrodes of the tube.

Another important feature consists in the use of an arrangement and procedure by which adjustment of the deformable electrode serves concurrently to establish the proper relationship between the remaining electrodes of the tube.

A still further feature, which is ancillary to those specified above, comprises the use of a multipart cathode construction of such nature that relative adjustment of the respective parts affords an effective means for bringing the active component of the cathode into precisely the proper correlation with the other electrodes. The features which I desire to protect herein are pointed out in the appended claims. The invention itself, together with further objects and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawings in `which Fig. l represents in section a three-element discharge tubeof a type which may suitably;Y be constructed in accordance with the invention; Figs. 2 and 3 represent successive steps in the process 4ofiabricating a tube such as that illustrated in Fig. 1; Figs. 4 and 5 represent optional steps in the process of completing the fabrlcation of the tube of Fig. 1-; Figs. 6 and 'l show an alternative method of procedure accordingto the invention; Fig. 8 illustrates the application of the invention to a form of device somewhat different from that illustrated in Fig. 1; Figs. 9 and 10 are enlarged detail views which illustrate various aspects of the structure of Fig. 8; Fig. 11 is a sectional view of a diode of a type which may be produced in accordance with the invention, and Fig. l2 shows an intermediate step in the fabrication of the tube of Fig. 11.

Referring particularlyto Fig. l the discharge tube there illustrated includes a series of three circular metal members I Il, II and I2 which are arranged in spaced relation and which are mutually separated by vitreous `(e. g'. glass) cylinders I3 and I4 sealed between them. Both the metal members ID to I2 and the cylinders I3 and I4 are of progressively decreasing diameter from one end of the tube to the other so that the tube as a whole has a step-wise coniiguration.

The metallic part I2 includes a planar portion I8 having a central opening I 9 and a circular rim 2U which extends away from the main body of the discharge enclosure. Within the opening I9 there is provided a cathode structure which includes a supporting part 24 and an active part consisting of a metal disk 21, a cylindrical sleeve 28 secured to the disk 21 and a flanged sleeve 29 Which depends from the disk. The disk is preferably coated on its upper'surface with an activating coating such as a layer of barium and Strontiumcarbonates, and a lamentary heater 32 arranged within the cathode structure serves to maintain the disk at a temperature of thermionic emission. In the use of the device, the heat developed by the filament 32 is conveyed to the emissive disk 21 both by direct radiation and by conduction through the sleeve 2g. 'I'he sleeve 29 serves the further function of minimizing radiation of heat to the other parts of the cathode structure. l

` The part 28, by which the emissive disk 21 is directly supported, is preferably constituted of a thin foil of a metal of low thermal conductivity such, for example, as a nickel-iron-cobalt alloy (Fernico) Because of the relatively limited heat conduction pathj provided by the foil, Whichmay be on the order of a few tenths of a mil in thickness, the loss of heatf from the disk 21 to the other part of the cathode structure is relatively slight, and eflicient operationof .the cathode is assured. The part 28 is of such dimensions that it may slide over the part 24,being prevented from moving with respect to that part, however, by a welded connection to it. (The cathode structure just specified, including particularly the combination of the heat shield 29 and the part 23 which provides high resistance to heat flow, is more fully described and is claimed in my copending application Serial No. 453,158, filed August 1, 1942, and assigned to the General Electric Company, a corporation of New York.)

For the purpose of supporting the cathode structure, a Series of relatively rigid conductors 38 are attached to the lower surface of va. circular flange formed on the part 24. The part 25 is arranged in face to face relation with the lower surface of the partl but is maintained at a fixed spacing with respect to this part by the interposition of a sheet or layer of a dielectric substance 42 consisting, for example, of mica or other inorganic insulating material. As a result of this arrangement the cathode structureA is insulated from the part I2 with respect to unidirectional currents while being effectively connected to -it (e. g. through the capacity between the opposed surfaces of the parts I8 and 25) as far as high frequency currents are concerned. As a consequence, the part I2 is adapted to serve as a high frequency terminal for the cathode structure.

Unidirectional potential may be supplied to the cathode and heating current may be supt plied to the filament 32 by means of the conductors 38 and additional Vconductors 43. connected-to the terminals of the lament. In the illustrated arrangement, these various conductors are sealed through a metallic closure 'member 44. VA centering pin 55 which depends from the kadaptor 53 serves to facilitate the orientation of the tube in a cooperating socket.

, The class cylinder I4 is sealed to the upper surface of the planar wall part I8 in a region .surrounding the cathode structure, the joint between these parts being vacuum-tight. In order to facilitate the production of a joint of this kind it is expedient to form the part I2 as well as the disks I0 and II of iron and to use for the cylinders I3 and' i4 a glass which is capable of being sealed to iron, such glasses being described, for example, inV Hull and Navias Patent No. 2,272,747, granted February 10, 1942. To make VJthe sealing process easier, the various metallic parts in question are preliminarily coat-ed with copper, which has they further effect of increasing the surface conductivity of these members with respect to high frequency currents. The

copper is to some extent oxidized during the sealing procedure and it is desirable to remove this oxide before putting .inv place the cathode structure and Ythe closure member 44 upon which the cathode structure is mounted. As a further preliminary" to evacuation of the device and sealing in of the closure Amember it .has been found helpfulin some cases to silver or gold plate the internal andr external surfaces of the parts I0", II and I2 to assure that these i solid cylinder 6B.

opening formed centrally in the disk I2 and contube enclosure.

4 surfaces shall be perfectly clean and resistant to corrosion.

The disk II which is sealed to the upper extremity of the cylinder I4 is provided with a central opening 5S and supports a mesh grid 51 covering this opening, the grid being spaced only a few mils from the active surface of the cathode disk l21. Above the grid and in cooperative relation with respect to the grid and cathode, there is supported an anode in the form of a This extends through an nects above the disk with a cylindrical terminal 6I which, as shown, is of smaller diameter than the disk Iil, although of larger diameter than the hole formed in the disk. A fused metal joint produced between the terminal 6I and the disk IIJ, as indicated at 62 renders this end of the tube vacuum-tight and completes the enclosure of the device.

In connection with a tube such as that described, it is extremely important that the spacing established between the various electrodes and especially the spacing between the cathode disk 21 and the grid 51, be maintained within very close tolerances and be substantially invariable from tube to tube. In order to fulfill this condition in a manner which is consistent with the requirements of quantity production methods, the present invention makes use of a procedure such as is illustrated in Figs. 2 and 3.

In the first of these gures there are shown certain tube parts which correspond to various parts illustrated in Fig. 1 and which are similarly numbered. These include particularly the enclosure-forming parts I0 to I4, the grid 51, and the cathode parts 24 to 29.

The parts IU to I4 and the grid 51 are already assembled in the relationship they are expected to occupy in the nished device. 'Ihese parts, together with the incompletely assembled cathode structure and a spacing cap "B9 interposed between the cathode disk 21 and the grid 51, are mounted upon a fabricating jig having an outer cylinder 10 which bears upon the cathode part 25 and a retractable plunger 1I which engages the lower extremity of the part 29. (At Vthis point no joint exists between the cathode parts 24 and 28, so that relative motion of these parts is possible.) A spring 13 located within theinterior of the jig structure tends to press the plunger 1I upwardly while a set screw 14 affords a convenient means for locking the plunger in a. particular location with respect t0 the body of the jig. The jig as a whole, and the parts which it carries are supported upon a fixed arm 16 extending outwardly from a bench 11V or other immovable working surface.

In place of the anode 60 referred to in conf nection with Fig. 1 the upper part of the tube contains a'location-determining agency 80 which is in substantially the same form as the anode 60 but'which differs in length from the anode by an amount corresponding to the spacing desired to exist between the active surface of the anode and the active portion of the grid 5,1. The part 8i) is provided at its upper end with an 'enlarged cap 82 which determines the distance which the part BIJ can project into Athe The cap 82has a still larger part 82 whichV is engaged by' a recess formed in a movable arm 84, and at its opposite ,end the arm 34 is secured -to the upper extremity of controlled pedal or actuator indicated at 81.

The `pedal 81 acts againsta spring 88 so that the plunger 815 is normally biased in the upward direction, but when pressure is applied to the pedal, the plunger and consequently the part 80 are :moved downwardly. Assuming the set screw 'I4 to be in a retracted position, the part 80 acting on the grid 51 will overcome the action of the spring I3 and will move the discharge enclosure downwardly until the part i8`comes to rest upon the upper surface of the insulator 42. When this condition is Vattained the supporting part 24 of the cathode structure is in substantially its intended relationship with reference tothe tube as a whole. Since further downward motion of the tube is impossible under the vcircumstances assumed, continued motion of the part 80 can occur only as a result of downward deformation of the grid 51 as indicated in Fig. 3. ifA the lforce applied is sufficient to cause such deformation to occur, the part 8i) will eventually reach the point at which the capV 82 is seated upon the upper surface of the disk It. If subsequently the part 80 is replaced by an anode which diiers from it only in being a: mils shorter, it is clear that a spacing of exactly :c mils will exist between the anode andthe deformed central portion of the grid l. This then affords an extremely accurate method of obtaining a desired spacing between the grid and anode in a construction such as that illustratedY in Fig. 1. In a particular case a spacing of about 13"mils has been found appropriate.

To obtain an equally accurate spacing between the grid and the active part of the cathode structure, it is only necessary to make the cathode-grid spacer 69 of the proper dimensions. In general,

. it is found desirable to apply the activating coating to the cathode disk [il after the cathode assembly is completed so that the spacer E9 should have a thickness equal to the desired cathode to grid spacing (say, 4 mils) plus one or two mils to take into account the expected thickness of the subsequently deposited layer of activatingmaterial.`

With the spacer 69 in place, the upward pressureof the spring 'i3 (Fig. 2) serves to maintain the spacer clamped between the grid and cathode surfaces as the grid is deformed downwardly and thus holds a constant spacing between these surfaces. This spacingwill he retained even when 'the part 80 moves to its lowest permitted position (i. e. the positionillustrated in Fig. 3). Accordingly, if the cathode structure is frozen in the relationship which it then occupies, the` desired relationship between the cathode and the grid and anode elements will have beenestablished. This freezing of the cathode parts can be accomplished by adjusting the set screw 14 so that it clamps the parts 7G and 'H in fixed spatial relationship and then removing these elements from the tube assembly together with the cathode parts which they respectively support. Without disturbing this arrangement, the cathode foil 28 may then be welded to the outer surface of the part 2d so that no subsequent displacement between them is possible. The spacer 69 may then be 'removed and the cathode Vreinserted into the tube assembly with the certainty that its active surface will occupy the desired relationship with respect to the grid 51.

lmakes it certain that the earlier disposition of the cathode structure in the discharge enclosure can be accurately reestablished.)

`It occasionally happens that in welding the (The fact that the part 42` abuts atly against the under surface of the part` parts of the cathode structure together, some slight displacement of these parts may occur in spite of the fact that they areretained very closely in their proper relationshipby the jig elements 10 and 7l. If any displacement of this kindlhap-` pens, it can be readily rectified by replacingythe cathode structure in the lining up assembly shown in Figs. 2 and 3. If this is done and the part 80 is again forced downwardly into its lowest possible position, it will reestablish the 'desired reiationship of the various elements. In some cases it may be desirable to substitute for the element "it a similar element having a length a fewgmils greater so that it is capable of producing a slight additional deformation of the grid 5l. When such a longer element is forced down into the tube assembly it will obviously seat the grid firmly upon the spacer 69 even if some slight shrinking ordeformation of the cathode structurehas occurred. If no such shrinkage exists, the slight additional displacement of the grid will be taken up by a correspondingly slight deformation or compliance of the foil of which the cathode part 28 is constituted. It is assumed thatthe cathode parts 2e and 28 are welded in iixed relationship at this point so that relative displacement between them is no longer possible, The details of this realigning step are indicated in Figs. 4`and 5 in which the displacement between the"dotted lines a and b represents the difference inv length between the location determining agency 8i) originally employed and theslightly longer element 8d employed in the realigningproces's; Spot weids joining the cathode part 28' tothe part 2d are indicated at 95 in Fig.

After the assembly of the cathode parts and the rechecking of the cathode to grid spacing has been accomplished, the cathode filament 32 (Fig. l.) is inserted in its proper location and the cathode structure as a whole is mounted upon the closure member 44 (i. e. by means of the con-` ductors 38 and d3). Finally the closure member is soldered to the lower edge of the circular flange Eil by a mass of solder 45 as previously specified.

The flange 2i) is of such dimensions with relation to the length of the `conductors Sethat it does not seat upon the surface of the closure part 44 but remains slightly spaced from it while the soldered Joint is being produced. This means that the cathode part 25 can lbe forced firmly against the insulating disk i2 y be seated solidly upon the envelope part i8. ccordingly, assurance is provided that the cathode structure as a whole occupies precisely the relationship which it had during its preliminary' adjustment (i. e. during the performance of theprocedural steps illustrated in Figs. 2 and 3.)

In some Vcases itis desirable to omit the insulating disk l2 and to solder thecathode part 25 directly to the envelope part I8. Where this is done, the preliminary line-up procedure will be the same as that described in the foregoing eX- cept thatthe part 25 will be seated against the part la during the deformation of the grid 5l.

It is not necessary that the means employed to determine thespacing between the anode and the grid 51 shall take the precise Aform represented in Figs. 2 and 3. Alternatively, one may employ the anode` itself in connection with a spacerof appropriate dimensionsused in the manner of the spacer 69. Of course,.where such a spacer isernployed, it must be capableof attachmentto the lower extremity'of the anode andthe opening formed in the disk. i0 `must be of sufficientdiar'nef-k and' that the disk in turn can I spacer and its attaching means.

As a further alternative-to forming the grid by use of an anode-simulating element, as described in connection with Fig. 2, the same functionmay be accomplished by appropriate manipulation of the cathode parts as indicated in Fig. 6. (In this figure, parts corresponding to elements previously described bear similar reference numerals differentiated by priming.) In the intended location of the anode there is provided a location determining agency which diiiers from lthe anode in by an amount corresponding to the desired spacing between the anode and grid, the intended length of the anode being indicated by the dotted line I0|. The grid 51 is pressed upwardly against the lower extremity of the element |00 by pressure suitably applied to the lower extremity of a plunger 1|' which acts upon the cathode sleeve 29'. This drives the active part of the cathode structure in an upward direction, carrying with it a spacer 69 which acts against the lower surface of the grid to deform it. Upward pressure is applied to the jig and downward pressure to the part |00, as indicated by the arrows A and B respectively, so that all the elements of the tube structure are placed under compression. A completed discharge device formed in accordance with the procedure illustrated in Fig. 6 is shown in Fig. '1, the lower part of the tube being broken away to conserve space.

The invention may also be applied in connection with the fabrication of a tube in which the cathode takes the form of a directly heated filament rather than an indirectly heated construction as in Fig. 1. This possibility is illustrated for example, in Figs. 8, 9 and 10, the last two gures showing the structuralv details of a completed cathode structure of the type in question.

As appears most clearly in Fig. 10` the cathode includes a supporting part IIII which is in telescoping relation with a metallic sleeve I I forming the lower component of the active part of the cathode structure. The emissive portion of the cathode is in the form of a V-shaped lament ||3 (Fig. 9) which extends across the upper face of the cathode structure. The laments which make up the sides of the V rest at their extremities upon the upper surface of a mica washer ||5 which is held in place by the fact that the edge of the part is crimped over to provide a retaining means as indicated at IIS. (The upper edge of the part -is cut away at appropriate regions to avoid interference with the filament I3.) The apex of the filament V is engaged by a spring arm I |8, whereas the extremities of the V are attached appropriately formed terminals ||9 and |20. These terminals are clamped between the mica washer I5 and a second similarly shaped mica washer |22 positioned below it, the inwardly extending parts of the terminals being shown in Fig. 10. Current is supplied to the filament by wires |24 which connect with lead-in conductors |25 shown only in part. The supporting structure for the cathode is quite similar to that described in connection with Fig. l and includes a circular flange |30 which bears against an insulating washer I3 I the washer in turn being pressed against the lower vsurface of a metallic envelope part |32. The upper end of the cathode, specifically the filament ||3, is, in the completed form of the tube, desired to be spaced a particular distance from the grid |35 (Fig. 8). In order to produce the desired grid-to-cathode spacing, aspacer capl |38 is placed over the upper end of the cathode so that it lies flat upon the filament I |3 being supported through the iilamentbyi the underlying mica ring I|5. As in the procedure described in connection with Fig. 2,'a locationdetermining agency |40 having a particular dimensional relationship to the anode which is to be used in the tube is forced down against the grid |35 to produce a predetermined deformation of it. After this operation is performed, the cathode parts ||0 and are locked in the position which they then occupy by means of a jig having an outer component |42 and an inner, relatively movable component |43, these being adapted to be secured in Xed relation by a set screw or other means, not shown. With the jig in locked relation, the cathode structure (after adjustment) is removed from the tube assembly and its parits welded together in the manner previously described. Thereafter, upon removal of the spacer' cap |38 and restoration of the cathode structure toits original position in the tube assembly, the desired fixed spacing between the cathode filament and the grid |35 will have Vbeen attained. The desired spacing between the anode and the grid is, of course, produced by substituting for the location-determining element |40 an anode whose length differs from that of the element by the desired amount.

Certain aspects of the invention are Valso applicable in connection with the fabrication of two Y element 'discharge tubes. This is illustrated in Figs. 11 and 12 which show respectively a oompleted diode of a type described in my Vcopending application S. N. 436,633, and an intermediate step in the manufacture of such a diode.

The tube referred to includes an apertured circular part |48 having an indirectly heated cathode extending through its central opening. As in the construction of Fig. 1, the cathode comprises an active disk |40 to which is secured a depending sleeve |50 and a cylinder of metal foil I5|, the cylinder being telescoped over and welded to a correspondingly shaped suporting part |52. A iilamentary heater |53 is provided within the interior of the cathode, being supplied With heating current by means of lead-in terminals |55. Additional lead-in conductors |56 are provided for the purpose of supporting the cathode structure and supplying it with unidirectional potential.` Close capacitive coupling between the cathode Vstructure and the part |50 is provided' by means of a flat metallic member |55 which is connected to the cathode and which is insulatingly spaced from the part |50 by means of a@V mica spacer |60.

is closed .by means of a generally cup-shaped part I5! which is reverse'ly bent to provide a circumferentially extendingtrough portion |52.V This latter portionA is adapted to receive the extreme edge Vof the member |40 and when filled with solder as indicated at |03 provides a vacuum-tight seal -for the tube enclosure. The lead-in wires |55 and |56 aresealed through the part |6I by means'of a plurality of glass-to-metal'seals shown at |64.

` The lower edgeof the cup-shaped part IBI is provided with bent-in tabsV |06 which serve to engageand'retain a socket adapter |61 constituted of a suitable insulating material, such as a synthetic resin. The adapter is provided with a centering lug |61" and supports a number of hollow contact prongs |58 towhich the Vextremities'l of the conductors |55 and |56 are attached.

The anode of the device' comprises a disk |60 which issupported in fixed spaced relation with respect tothe active surface of the cathode by being sealed to the end of a glass cylinder |10.

In the fabrication of the tube the anode |69 and the base part |48 are first sealed to the respective extremities of the glass cylinder |'|0. Thereafter these elements and the loosely assembled cathode parts are positioned in a line-up jig having a fixed part |80 and two concentric movable parts |8| and |82. (See Fig. 12.) At this stage, the insulating disk is omitted for a reason which will shortly appear. By pushing the jig parts IBI and |02 concurrently in the up- Ward direction, the ange of the cathode part |52 is caused to seat atly against the under surface of the part |48 `and the cathode cap |49 is pressed against the anode |69.

A Thereafter, the cathode assembly is frozen (by Vlocking the jig parts `|8| and |82 together) and withdrawn from the tube so that the cathode parts may be welded in xed relationship Finally, the cathode is mounted on the base |"6| and reinserted in the tubein the arrangement shown in Fig. 11, the insulating washer |60 being now included. By comparing Figs. 11 and 12 it will be seen that the resultant spacing of the cathode with respect to the anode |69 corresponds precisely to the thickness of the Washer, which may be made asgreat as is desired for the particular application at hand.

In cases where the cathodestructure and the base part |50 of Fig. 11 are desired to be at the same potential, a metal Washer may be used as a spacer in place of the insulating disk |60. As a still further variant, in a case where the anode is of the type employed in the construction of Fig. l, the desired anode-cathode spacing` may be obtained by inserting a washer of proper thickness under the anode terminal cap after the anode and cathode have been brought into abutting relation and the cathode parts joined in accordance with a procedure such as that just described.

While the invention has been described by specifying various procedural steps as being taken in a particular order, it will be understood that a considerable variation in the order of procedure is possible, and I aim in the appended claims to cover all such equivalent variations as come within the true spirit and scope of the foregoing disclosure. a

VWhat I claim as new and desire to secure by Letters Patent of the United States is:

1. A process of fabricating a discharge device having an electrode of deformable construction, which process comprises installing the electrode approximately in its desired location in the device and thereafter deforming the electrode in situ to bring its active part more precisely into the desired location.

2. A process of fabricating a discharge device having a grid constituted of deformable material, which process comprises installing the grid approximately in its desired location in the device, and thereafter deforming the grid in situ to bring its active part more precisely into the desired location.

3. A methodl of fabricating a discharge device having an electrode of deformable construction, which method comprises installing said electrode in approximately its desired location in the device, positioning location-determining agencies on opposite sides, of said electrode, and deformingA the electrode by said agencies, thereby to effect a more precise location of a part of said electrode.

4; Afmethod of fabricating an electric discharge device having a first electrode structure and a second electrodestructure which includes an active part and a supporting part; which method comprises installing said rst electrode structure in its desired location in the device, placing said secondstructure in approximately its desired location in the device and with its parts in loose assembly, moving said parts relative to one another into precisely their desired relationship with respect to said first structure, and thereafter joining said parts in fixedassembly to assure the subsequent preservation of the said relationship.

5,. The method of fabricating a discharge device having a first electrode structure of deformable character and a second electrode structure which includes the assembly of an active part and a supporting part; which method comprises installing said first structure in approximately its desired location in the device, installing said second structure in approximately the desired relationship with the rst structure and with its parts in loose assembly, deforming the said first structure to bring it more precisely into the desired 1ocation, modifying the assembly of said second structure to bring its active part more precisely into the desired relationship with the iirst structure, and thereafter fixing the assembly of the second structure to preserve the said desired relationship.

6. The method of fabricating a discharge device having a generally planar grid constituted ofV deformable material and a cathode which in-V grid portion, and thereafter xing the assembly of said parts to assure the preservation of the said spacing.

'7. A method of fabricating a discharge device having an envelope, an anode, agrid of deformable material and a cathode which includes active and supporting parts capable of being assembled in engaging relation; which method comprises installing said grid in said envelope, positioning said active cathode part in substantially its proper relation to said grid, `arranging said supporting part of the cathode in its intended location with respect to said envelope and in loosely engaging relation with said active part, deforming said grid to bring it more precisely into its desired location, bringing the active part of said cathode structure more precisely into its proper relation to said grid by adjustment of such part with reference to the said supporting part, securing said cathode parts to one another in the relation which they then occupy, and finally completing the assembly of said device.

8. A method of fabricating a discharge device having an envelope, an anode, a grid of deformable material and a cathode which includes separate active and supporting parts capable of being mutually joined; which method comprises the following steps, installing the grid in said envelcpe in substantially its intended location, positioning the active cathode part in proximity to said grid with a spacer of predetermined thickness between them, arranging said supporting part in its intended location with respect to said envelope and in proximityvto said active part, deforming a portion of said grid to bring it more preciselyinto its desired location, moving said active cathode part with reference to said supporting part to establish between said active cathode part and the deformed portion of said grida spacing determined by the thickness of sald spacer, joining saidv cathode parts in the relation which they then occupy, removing said spacer, and completing the assembly of said device.

9. A method of fabricating a discharge device having three electrodes, the intermediate electrode being a grid of deformable material, which method comprises temporarily assembling said grid and a selected one of said remaining electrodes in approximately their desired relationship in the said device, interposing between said Y electrodes a vspacer having a thickness equal to the desired spacing of the electrodes, adding t0 the assembly an agency having a surface which can be located with certainty in a plane which is a fixed distance from the desired location of the third electrode, moving said surface against the grid to bring the active part of the grid into the said plane while said spacer maintains the grid in fixed relationship with respect to said one electrode, and thereafter withdrawing said spacer and said agency and completing the permanent assembly of the electrodes.V

10. A method of fabricating a discharge device having a first electrode which is of deformable character and. a second electrode, which method comprises installing said electrodes 1n approximately the desired location in the device,

interposing a spacer of predetermind dimensions between the electrodes, and moving said second electrode to force said spacer against the first electrode with resultant deformation of it, thereby to bring the active parts of both said electrodes more precisely into the desired location in said device while concurrently establishing a desired spatial relationship between them.

11. The method of -fabricating a discharge device having three electrodes, the intermediate electrode being constituted of deformable material, which method comprises temporarily assembling said intermediate electrode and a'selected one of the remaining electrodes in approximately their desired relationship in the said device, interposing between said electrodes a Spacer having a thickness corresponding to the desired spacing of the electrodes, adding to said assembly anagency having a surface which can be located with certainty a` fixed distance from the desired location of the active surface of said third electrode, moving said selected electrode toward said intermediate electrode without withdrawing said spacer, thereby by deformation of material to force the active portion of said intermediate electrode against the said surface of said agency while maintaining the desired spacing of said selected and intermediate electrodes, and thereafter withdrawing said spacer and said agency completing the permanent assembly of the electrodes.

12. A method of fabricating a discharge device having three electrodes including a grid and cathode of deformable character and an anode of non-deformable l character, which method comprises temporarily assembling said grid and cathode in approximately their desired location in said device with a spacer of predetermined ode by the action ofsaid spacer to preserve-a:

fixed spacing between the grid and cathode and thereafter withdrawing said spacer andV said agency and completing the permanent-assemblyof said electrodes. Y

13. A method of fabricating a discharge d e- Y vice having a first electrode and a second elec-- trode which includes as separable componentsy an active part and asupporting part; said method comprising the steps of disposing said-.iirst electrode in its desired location in said device,y

disposing the supporting `part of said second.V

electrode at a fixed distance from the first electrode and in approximately its desired relationship with respect to such electrode, arranging the active part of said second electrode in abutment with said first electrode and in its desiredl relationshiprwith respect to said supporting part, fixing said active and supporting parts in the relationship which they then occupy, displacing the whole structure of one of saidrelectrodes from its originally assigned location byv an amount corresponding to the spacing desired to exist between the said active part yand the first electrode, Vand without subsequnt displacement of the parts completing theiixed assembly of the device. v v

14. A method of fabricating a discharge device having a cathode which includes. an active part and a supporting partadapted to be assembled in telescoping relation,Y a second electrode adapted to cooperate with said cathode, and anl envelope for enclosing said cathode and saidV second-electrode; said method comprising disposing said second electrode in its desired location in said envelope, disposing said cathode in the envelope with its parts in loosely engagingassigned location in the envelope by an amount corresponding to the spacing desired to exist between the anode and cathode, and without subsequent change in -the relationship 0i" the parts completing the permanent assembly of the device.

l5. A method of fabricating an electric discharge device having a first electrode structure and also having a second electrode structure which includes a cylindrical supporting part and a conformingly cylindrical active part; which method comprises installing said iirst electrode structure in its desired location in the device, placing said second structure in approximately its desired location in the device with its said cylindrical parts in slidably interiitting relation, relatively sliding said parts to cause the said active part to assume precisely a desiredY spacing with respect to said first electrode structure, and thereafter fixing the assembly of said parts to assure the preservation of the said spacing.

JAMES E. BEGGS. 

